[PATCH] D133396: [MemorySSA] Don't do addr phi translation if addr value is not a loop invariant

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

You need to update phi-translation.ll for this change. From a cursory look I think the results improve while still being correct.



================
Comment at: llvm/include/llvm/Analysis/MemorySSA.h:1258
             Location.getWithNewSize(LocationSize::beforeOrAfterPointer());
-      PHITransAddr Translator(
-          const_cast<Value *>(Location.Ptr),
-          OriginalAccess->getBlock()->getModule()->getDataLayout(), nullptr);
-
-      if (!Translator.PHITranslateValue(OriginalAccess->getBlock(),
-                                        DefIterator.getPhiArgBlock(), DT,
-                                        true)) {
-        Value *TransAddr = Translator.getAddr();
-        if (TransAddr != Location.Ptr) {
-          CurrentPair.second = CurrentPair.second.getWithNewPtr(TransAddr);
-
-          if (TransAddr &&
-              !IsGuaranteedLoopInvariant(const_cast<Value *>(TransAddr)))
-            CurrentPair.second = CurrentPair.second.getWithNewSize(
-                LocationSize::beforeOrAfterPointer());
-
-          if (PerformedPhiTranslation)
-            *PerformedPhiTranslation = true;
+      else {
+        PHITransAddr Translator(
----------------
A slightly more accurate check would be `if (Location.Size != LocationSize::beforeOrAfterPointer())`. If the size is already unknown originally, then we don't need to bother with phi translation either.


Repository:
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  https://reviews.llvm.org/D133396/new/

https://reviews.llvm.org/D133396